Harden API / add a LOT more unit tests

[iskra-anl]

In GitLab by @perarnau on Aug 13, 2019, 10:13

The unit tests need a good cleanup, to become quicker and more exhaustive. Things I've noticed:

• bitmap tests are too slow, and not very smart (checking that every bit can be set is not really necessary)
• dma and scratchs are missing corner cases: invalid arguments, destroy too early, cancels in the middle of operations

[iskra-anl]

In GitLab by @perarnau on Aug 13, 2019, 16:43

mentioned in merge request !74

[iskra-anl]

In GitLab by @perarnau on Jan 28, 2020, 10:18

Additional comments:

• a lot of the generic API is not tested against new layouts.
• layout-pad-row-major not validated